Competing polkit authentication agents

I'm running OpenSUSE Leap 42.2 on my desktop and both my notebooks. After the last system update, one of the notebooks started to show the following Error dialog after logging into LXDE:

GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: An authentication agent already exists for the given subject

Googling for the message didn't help much, so I had to start experimenting myself. Comparing the output of ps -eo euser,pid,cmd | grep [p]olkit on different devices showed the notebook had one more line there:

polkitd 1657 /usr/lib/polkit-1/polkitd --no-debug
choroba 2283 lxpolkit
choroba 2308 /usr/lib/polkit-gnome-authentication-agent-1

The extra line was the last one.

I had no idea who started the gnome agent, and I wasn't able to find out quicky: pstree shows systemd as its parent.

Nevertheless, I was able to prevent it from running. In the file /etc/xdg/autostart/polkit-gnome-authentication-agent-1.desktop, I changed the line

NotShownIn=KDE;

to

NotShownIn=KDE;LXDE;

The error is gone.

Upgrading to openSUSE 12.2 with LXDE.

I upgraded my home computer to openSUSE 12.2. I use LXDE as my desktop environment. So far, I noticed two annoying bugs, but fortunately found workarounds for both of them.

1. It is not possible to logout from LXDE properly. Or, better to say, after the logout, the X server is not restarted. You have to switch to a text console and rerun lxdm manually as root. I was not able to find a simple fix, so I switched to lightdm which does not have the problem.

2. Firefox was showing a warning each time I started it: it was not able to connect to the DBus. After some googling and hacking, I discovered a rather simple solution. Just prepend the following line to your
~/.config/lxsession/LXDE/autostart:

    export `dbus-launch`